> our bodies also figured out that for an extended period of time this ability was useless since vitamin C was so readily available in all our food sources in most circumstances
But none of the other animals in our biomes similarly optimized? Including none of the other apes?
The less Panglossian interpretation is a gene got fucked up, it didn't wipe us out, and the fuck-up got conserved because it doesn't kill us before reproduction, it just makes us sicker from time to time.
Fascinatingly, we could biohack our way into having the human liver produce vitamin c, like we have the science to do that. It's just an insane amount of risk compared to just eating an orange once in a while.
All apes cannot produce vitamin C. In fact no dry nosed primates can. Also fruit bats generally can't, as well as some passerines, and some bony fish.